President Trump’s announcement that he will not impede the release this week of the last known government files on the 1963 assassination of President John F. Kennedy excited scholars and casual conspiracy theorists who believe the truth behind the Dallas shooting has never come to light.

But historians and experts don’t expect bombshell revelations about what unfolded on Dealey Plaza.

“I don’t think there’s going to be [information] in there pointing to a second gunman, or anything like that,” said Philip Shenon, author of “A Cruel and Shocking Act: The Secret History of the Kennedy Assassination.”

Advertisement

Shenon said the documents would probably reveal that both the CIA and FBI had additional information about Lee Harvey Oswald than has been previously known.

Get Metro Headlines in your inbox:

The 10 top local news stories from metro Boston and around New England delivered daily.

“I don’t think there’s going to be any big surprise in this. It kind of depends on what the president decides to do, if he decides to protect any of the information further,” said John R. Tunheim, chief judge of the US District Court of Minnesota, who chaired the Assassination Records Review Board in the 1990s.

Under a law passed in 1992, Congress decreed that all assassination documents be stored at the National Archives and Records Administration, which is now home to more than 5 million pages of records and other artifacts.

Trump tweeted this weekend that he did not intend to further delay the release of the records, which under that 1992 law is mandated for this Thursday.

However, the White House left the door open this week to blocking the release of some of the documents if intelligence agencies offer compelling national security or criminal justice arguments against their publication.

Advertisement

“I’m not at all convinced that Trump is going to allow everything to be released — my guess is that he’ll still hold something back,” Shenon said.

Which files are being released? What has already been released?

About 1 percent of the files remain concealed. Another 88 percent were published by the late 1990s, while some 11 percent have been released but with redactions, according to the National Archives.

What could these papers tell us?

Experts say the documents, while unlikely to fundamentally alter the debate around the assassination, will probably answer long-running questions — particularly about Oswald’s background. The documents that could emerge this week could hold tantalizing details for those suspicious that the full truth about the government’s involvement after the assassination has never emerged.

“The coverup was never about the crime; the coverup was always about Oswald’s relationship with the FBI and the CIA, before the crime,” said John A. Farrell, a historian who has written biographies about former House speaker Thomas P. “Tip” O’Neill and former president Richard M. Nixon, and is now working on a book about the late Senator Edward M. Kennedy.

Of particular potential interest regarding Oswald is a trip he took to Mexico City before the assassination, meeting with Soviet and Cuban officials and drawing the interest of CIA agents in Mexico City.

Advertisement

Shenon called the Mexico City visit “the great secret chapter of the Kennedy assassination,” adding that CIA monitoring of Oswald while he was there should have triggered alarms in the United States that could have prevented the murder.

“That’s how the narrative of the assassination has changed over the years, from Oswald was this lone gunman who couldn’t be stopped, to the CIA and FBI actually knew a lot about Oswald before the assassination,” he said.

Oswald also lived in the Soviet Union for more than a year, a period that has drawn interest due to its suggestion of Cold War influence over the assassin.

“I’ve always suspected that whatever stuff they’re holding is that kind of material, talking about Oswald’s days in the USSR and when he came back, and what he was reporting to the FBI and what the CIA knew about him at the time of the crime,” Farrell, a former Globe reporter, added.

Shenon said, “The question in my mind has always been: Didn’t the CIA have evidence that Oswald was a threat?”

Who’s really interested in this?

Conspiracy theorists have remained skeptical that the official explanation — proffered by the Warren Commission in 1964 — that Lee Harvey Oswald acted alone is true.

But Tunheim and others said that the document dump is unlikely to provide resounding evidence to the contrary. Insight into Oswald, who himself was gunned down two days after JFK by Dallas nightclub owner Jack Ruby, could be the windfall.

If there are no bombshells, why has it taken 55 years for some of these to see the light of day?

Of the material that his review board kept secret in the 1990s, Tunheim said, “A lot of it has to do with intelligence gathering methods, and particularly arrangements with foreign governments for intelligence gathering, and that was still very sensitive in the 1990s.”

“My recollection is that we protected nothing that was central to the assassination story,” Tunheim said, adding, “What we were largely protecting was details of arrangements with foreign governments.”

What else is still out there?

Foreign governments also kept tabs on Oswald, and there is no timetable for the release of those documents, Tunheim said.

“A much more interesting group of files if we could ever get them released are the Oswald surveillance files, which sit in Minsk,” the capital of Belarus, Tunheim said. Further, files from the KGB — the former Soviet intelligence service — would probably shed further light.

“Anything about Oswald is, of course, of great interest to researchers,” he said. “There probably are gems in that file that will probably help people better understand Oswald.”

Shenon said transcripts of interviews conducted for “The Death of a President,” William Manchester’s 1967 book, remain under the control of the Kennedy family.